Multiple Registrations Issue

Unidata phones have an issue in regards to responding appropriately to phone calls placed to a user that has more than one device (when the call is forked). The behavior of the phone is not compliant with SIP RFC 3261 or with OnSIP.

As an example, we registered a SQ3000 to hiro@example.onsip.com. Hiro makes a phone call to charlotte@junctionnetworks, who is registered on a Polycom 550 and an Eyebeam. The SQ3000 hears first from the Polycom and then the Eyebeam. If Charlotte picks up the Polycom, the phone call will complete appropiately. However, if Charlotte picks up the Eyebeam instead, the SQ3000 continues to ring and Charlotte hears silence.

This bug is repeatable with any combination of phones that we tried - the SQ3000 always ignores the second phone that it hears from.

We have notified Unidata of our findings and they have acknowledged that the phone cannot reliably complete calls where responses are received from multiple to destinations due to a forking proxy and as such the phone is not compliant with the core SIP RFC 3261, but are unaware of any time frame in which this bug will be fixed. Until such time, we do not advise the purchase of Unidata phones.